The present invention relates to a process for preparing areas of a substrate and/or electronic component for selective metal deposition on the thereon, more particularly to the use of a directed energy source to alter the surface of a substrate and/or electronic component under the exposed energy source from an inactive area to an active area for subsequent selective deposition of a metal on that surface of the substrate and/or component.
Laser and other directed energy sources such as ion and electron beams have been used to deposit and etch materials on surfaces for the purpose of forming localized regions of special chemical properties so as to facilitate the formation of metallic interconnections, such as between integrated circuits. Various prior known techniques for forming interconnections on substrates and components are exemplified by the following.
U.S. Pat. No. 3,506,545 issued Apr. 14, 1970 to R. L. Garwin et al. discloses heating a substrate which has both amorphous and crystalline states, such that heating of the amorphous state locally via a focused and programmed electron beam or laser beam, cause a change to the crystalline state, a higher conductivity state, whereafter electroplating of metallic conductive patterns can be carried out, since the crystalline state is conductive for electroplating current.
U.S. Pat. No. 4,217,183 issued Aug. 12, 1980 to R. L. Melcher et al. discloses a method for locally enhancing electroplating rates wherein the deposition occurs simultaneously with the heating of the substrate by a laser beam or other energy source, due to the heated portion being more readily electroplated than the unheated portion.
U.S. Pat. No. 4,574,095 issued Mar. 4, 1986 to T. H. Baum et al. discloses a process for selectively depositing copper by first selectively depositing palladium seeds on a substrate by irradiating a palladium compound with light, such as a laser, whereafter copper is deposited by an electroless process on the seeded area.
U.S. Pat. No. 4,701,347 issued Oct. 20, 1987 to G. S. Higashi discloses a method for growing patterned metal layers on a substrate by illuminating and heating the substrate with laser light in the presence of a metal-containing gas whereby metal-containing molecules are adsorbed on the substrate, whereafter the metal present on the surface catalyzes the growth of additional metal.
U.S. Pat. No. 4,983,250 issued Jan. 8, 1991 to J. T. Pan discloses a method of laser patterning an electrical interconnect wherein the interconnect is formed by applying an adhesion layer over a substrate, applying an electrical conductor layer over the adhesion layer, and applying a reacting layer over the electrical conductor layer, whereafter a laser beam is directed over the reacting layer in a desired pattern to interdiffuse the reacting and conductor layers and form a reaction product which is used as an etch mask for etching away the reacting, conducting, and adhesion layers located outside the reaction product.
U.S. Pat. No. 5,098,526 issued Mar. 24, 1992 to A. F. Bernhardt, assigned to the assignee of the present application, discloses a process for preparation of a seed layer for selective metal deposition, which involves formation of an initial surface on a substrate comprised of at least two layers with the uppermost layer being an electrical insulator, exposing the formed surface to a source of heat, such as laser energy, in pre-determined places wherein surface activation is desired causing melting and intermixing of the layers, and depositing metal on the activated portions of said surface, thereby forming metallic interconnects on the substrate.
While the above-referenced examples of prior techniques for forming interconnections on substrates and electronic components have produced effective results, there is a continuing need for more efficient and effective methods for the formation of electronic circuits or interconnects for electronic components, which can also be performed on a very small scale. The present invention is directed to fulfilling that need, wherein a surface is altered from an inactive to an active state for subsequent selective deposition of a metal on that altered surface.